1. Field of Invention
The present invention relates to a continuously variable valve timing apparatus. More particularly, the present invention relates to a continuously variable valve timing apparatus which may adjust the timing of the opening and closing of valves.
2. Description of Related Art
Generally, a continuously variable valve timing apparatus (CVVT or Camshaft phaser) is a device which may adjust the timing of the opening and closing of valves.
A general continuously variable valve timing apparatus usually used in vehicles, i.e. a vane-type variable valve timing apparatus, needs relatively small volume and is economical.
The vane-type variable valve timing apparatus, however, uses lubrication oil of an engine, and thus, when oil pressure is low, rapid and accurate control cannot be expected.
Particularly, in idle state, in high temperature, in start condition and in other situations, when engine oil pressure is not sufficient, relative phase change of a camshaft cannot be obtained, and excessive exhaust gas is generated.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.